Can patients safely discontinue oral anticoagulant therapy 6 months after an "unprovoked" or spontaneous episode of venous thromboembolism (VTE)? Researchers investigating this question say yes-if the patient is a woman with no more than one risk factor. This is a departure from current guidelines, which call for indefinite use of an anticoagulant, typically warfarin (Coumadin), following VTE.

The study involved more than 600 men and women who'd had a first, unprovoked major VTE. Researchers evaluated 69 factors that could contribute to recurrent VTE and narrowed the list to four factors that greatly affect the chances of recurrence in women: hyperpigmentation, redness, or edema of a leg; elevated d-dimer (greater than or equal to 250 micrograms/L while taking warfarin); a body mass index of 30 kg/m2 or higher; and being age 65 or older.

Women who had none or just one of these factors had only a 1.6% chance of developing another clot in the next year, compared with a 14.1% risk for women with two or more of these risk factors. Surprisingly, however, the researchers found no predictive factors that apply to men.

Researchers plan to perform a second study involving 3,000 people to validate their findings.